Thiophene compounds for liquid-crystalline media

ABSTRACT

The invention relates to liquid-crystalline compounds of the formula I 
                         
in which
         R 1 , R 2 , A 1 , A 2 , A 3 , A 4 , Z 1 , Z 2 , Z 3 , V, a, b and c have the meanings indicated in Claim  1 , and to liquid-crystalline media comprising at least one compound of the formula I, and to electro-optical displays containing a liquid-crystalline medium of this type.

The invention relates to thiophene derivatives containing adifluoromethyleneoxy group and to the use thereof as component(s) inliquid-crystalline media (LC media). In addition, the present inventionrelates to liquid-crystal and electro-optical display elements whichcontain the liquid-crystalline media according to the invention.

In recent years, the areas of application of liquid-crystallinecompounds have broadened considerably to display devices,electro-optical equipment, electronic components, sensors, etc., ofvarious types. For this reason, a number of different structures havebeen proposed, in particular in the area of nematic liquid crystals. Thenematic liquid-crystal mixtures have to date found the broadest use inflat display devices. They have been employed, in particular, in passiveTN or STN matrix displays or systems having an active TFT matrix.

The compounds according to the invention can be used as component(s) ofliquid-crystalline media (LC media), in particular for displays based onthe principle of the twisted cell, the guest-host effect, the effect ofdeformation of aligned phases DAP or ECB (electrically controlledbirefringence), the IPS (in-plane switching) effect or the effect ofdynamic scattering.

Various compounds containing a difluoromethyleneoxy bridge asliquid-crystalline material and the preparation thereof have beendescribed, such as, for example, in the specification EP 0786445 A1.

Thiophene derivatives have occasionally been investigated asliquid-crystalline substances. EP 0467260 A2 discloses compoundscontaining a 2,5-thiophenediyl unit. However, the compounds arepredominantly smectic. Modern display applications use mostly nematicliquid-crystal media.

The present invention was based on the object of finding novel stablecompounds which are suitable as component(s) of liquid-crystallinemedia. In particular, the compounds should simultaneously havecomparatively low viscosity and a dielectric anisotropy in the positiveregion. For many modern mixture concepts in the area of liquid crystals,it is advantageous to use compounds having high dielectric anisotropyΔ∈.

In view of the very wide variety of areas of application of suchcompounds having a high Δ∈, it was desirable to have available furthercompounds, preferably having high nematogeneity, which have propertiesprecisely customised to the particular applications.

One object of the invention was thus to find novel stable compoundswhich are suitable as component(s) of liquid-crystalline media, inparticular for, for example, TN, STN, IPS and TN-TFT displays.

A further object of the present invention was to provide compoundswhich, alone or in mixtures, have high dielectric anisotropy Δ∈ and ahigh clearing point. In addition, the compounds according to theinvention should be thermally and photochemically stable under theconditions prevailing in the areas of application. Furthermore, thecompounds according to the invention should have the broadest possiblenematic phase. As mesogens, they should facilitate a broad nematic phasein mixtures with liquid-crystalline co-components and be extremelyreadily miscible with nematic base mixtures, in particular at lowtemperatures.

Surprisingly, it has been found that the thiophene derivatives accordingto the invention are eminently suitable as components ofliquid-crystal-line media. They can be used, in particular, to obtainliquid-crystalline media which are suitable for TN-TFT or IPS displays.The compounds according to the invention are stable, even on exposure toair, and colourless. They are also distinguished by particularlystrongly positive dielectric anisotropies Δ∈, owing to which lowerthreshold voltages are necessary on use in optical switching elements.They have a broad nematic phase range alone or in mixtures. In addition,the compounds according to the invention have a particularly low meltingpoint, a high clearing point, and at the same time low values for therotational viscosity γ₁. Compared with substances from the prior artwhich have a similar property profile, a particularly low melting pointis observed, in particular, in the case of the compounds containingthree ring systems. The substances thus have a much lower tendencytowards crystallisation than corresponding conventional compounds. Thecompounds according to the invention can therefore be employed, forexample, in higher concentration.

The provision of the thiophene derivatives according to the inventionvery generally considerably broadens the range of liquid-crystallinesubstances which are suitable, from various applicational points ofview, for the preparation of liquid-crystalline mixtures.

The invention thus relates to compounds of the formula I

in which

-   R¹ and R² each, independently of one another, denote H, a    halogenated or unsubstituted alkyl radical having 1 to 15 C atoms,    where, in addition, one or more CH₂ groups in these radicals may    each be replaced, independently of one another, by —C≡C—, —CH═CH—,    —(CO)O—, —O(CO)—, —(CO)— or —O— in such a way that O atoms are not    linked directly to one another, where R² additionally and preferably    denotes F, Cl, Br, CN, SCN, NCS or SF₅,-   A¹, A², A³ and A⁴ each, independently of one another, identically or    differently, denote:    -   a) trans-1,4-cyclohexylene or cyclohexenylene, in which, in        addition, one or two non-adjacent CH₂ groups may be replaced by        —O— and/or —S—, and in which H may be replaced by F,    -   b) 1,4-phenylene, in which one or two CH groups may be replaced        by N, and in which, in addition, one or more H atoms may be        replaced by Br, Cl, F, CN, methyl, methoxy or a mono- or        polyfluorinated methyl or methoxy group,    -   or    -   c) a radical from the group 1,4-bicyclo[2.2.2]octylene,        piperidine-1,4-diyl, cyclobut-1,3-diyl,        spiro[3.3]heptane-2,6-diyl,

-   -   -   in which one or more hydrogen atoms may be replaced by F,            CN, SON, SF₅, CH₂F, CHF₂, CF₃, OCH₂F, OCHF₂ or OCF₃, one or            more double bonds may be replaced by single bonds, one or            more CH groups may be replaced by N,        -   M denotes —O—, —S—, —CH₂, —CHY— or —CYY¹—and        -   Y and Y¹ denotes Cl, F, CN, OCF₃ or CF₃,

-   V denotes H, F or Cl, preferable H or F,

-   Z¹, Z² and Z³ each, independently of one another, identically or    differently, denote a single bond, —CH₂O—, —(CO)O—, —CF₂O—,    —CH₂CH₂CF₂O—, —CF₂CF₂—, —CH₂CF₂—, —CH₂CH₂—, —(CH₂)₄—, —CH═CH—,    —CH═CF—, —CF═CF— or —C≡C—, where asymmetrical bridges may be    oriented to both sides,

-   a denotes 0, 1 or 2, preferably 0 or 1, particularly preferably 0,

-   b denotes 0, 1, 2 or 3, preferably 1 or 2, and

-   c denotes 0, 1 or 2, preferably 0,

-   where a+b+c≦4, is preferably equal to 1, 2 or 3, particularly    preferably 1 or 2.

A¹⁻³ and Z¹⁻³ may independently also adopt different meanings if theyoccur more than once for a, b or c>1.

The invention furthermore relates to the use of the compounds of theformula I in liquid-crystalline media.

The present invention likewise relates to liquid-crystalline mediacomprising at least two liquid-crystalline components which comprise atleast one thiophene derivative of the formula I.

The compounds of the formula I have a broad range of applications.Depending on the choice of substituents, these compounds can serve asbase materials of which liquid-crystalline media are predominantlycomposed; however, compounds of the formula I can also be added toliquid-crystalline base materials from other classes of compound inorder, for example, to modify the dielectric and/or optical anisotropyof a dielectric of this type and/or in order to optimise its thresholdvoltage and/or its viscosity.

In the pure state, the compounds of the formula I are colourless and,alone or in mixtures, form liquid-crystalline mesophases in atemperature range which is favourably located for electro-optical use.The compounds according to the invention can be used to achieve broadnematic phase ranges. In liquid-crystalline mixtures, the compoundsaccording to the invention increase the clearing point and significantlyincrease the polarity of the mixture.

Z¹ and/or Z³ preferably denote a single bond, —CF₂O—, —OCF₂—, —C₂F₄—,—CH₂O—, —OCH₂— or —(CO)O—, in particular a single bond. Z² preferablydenotes —CH₂CH₂—, —CH═CH—, —C≡C— or a single bond, in particular asingle bond.

In the case where Z² is a single bond, A² preferably denotes anunsaturated or aromatic ring from groups b) or c) in accordance with thedefinition of the formula I.

If present, A¹, A², A³ and A⁴ preferably denote

and furthermore

If present, the group A¹ preferably denotes

If present, A² preferably denotes

If present, A⁴ preferably denotes

R¹ preferably denotes alkyl, alkoxy, alkenyl or alkenyloxy having up to8 carbon atoms. R¹ particularly preferably denotes straight-chain alkylor alkenyl.

R² preferably denotes a polar radical X, where

-   X denotes F, Cl, OCF₃, OCHF₂, OCHFCF₃, OCF₂CHFCF₃, CF₃, CN, SF₅,    NCS, NCO, SCN, OCN,    -   in particular F, Cl, CN, CF₃ or OCF₃ and very particularly F or        OCF₃.

R¹ and R² preferably do not simultaneously denote H.

Particular preference is given to compounds of the formula IA

in whichR¹, A¹, X, a, b and V have the meanings indicated above for formula I,and L¹, L², L³ and L⁴ denote H or F.

Preference is given to compounds of the formula IA in which L′ denotesfluorine. b preferably denotes 1 or 2, in particular 1. V is preferablyH. L³ is preferably F. a+b is preferably 1 or 2. b is very particularlypreferably 1, and a is preferably 0. It is particularly preferred for 2,3 or 4 of the groups L¹ to L⁴ to be fluorine.

In a further embodiment of the invention, preference is given tocompounds of the formula I in which V denotes F. The compounds haveparticularly high dielectric anisotropy.

Particularly preferred compounds of the formula I are the compounds ofthe formulae I1 to I6:

in which R¹ and X have the meanings indicated above. L², L³, L⁴, L⁵, L⁶,L⁷ and L⁸ denote, independently of one another, H or F.

L², L³ and L⁴ particularly preferably denote, independently of oneanother, a radical F.

L⁵ and L⁷ preferably denote, independently of one another, H.

Examples of particularly preferred compounds are the following:

In the case of compounds which can occur in the form of diastereomers,both the pure substances and also any mixing ratio of the isomers areencompassed and are in each case to be regarded as suitable mixturecomponent.

The compounds of the formula I are prepared by methods known per se, asdescribed in the literature (for example in the standard works, such asHouben-Weyl, Methoden der organischen Chemie [Methods of OrganicChemistry], Georg-Thieme-Verlag, Stuttgart), to be precise underreaction conditions which are known and suitable for the said reactions.Use can also be made here of variants known per se which are notmentioned here in greater detail.

The compounds of the formula I can advantageously be prepared as can beseen from the following illustrative syntheses (Schemes 1 and 2):

The synthesis in accordance with Scheme 1 is based on a Suzuki coupling.

The synthesis in Scheme 2 is based on a known synthesis of the —CF₂O—group as indicated, for example, in the specification EP 1341742 A1.

The groups in the formulae in Schemes 1 and 2 which do not participatecan be varied so long as it is suggested by the definitions of thecompounds of the formula I. Corresponding starting materials cangenerally readily be prepared by the person skilled in the art. Thus,the compounds of the formulae I and IA can be prepared.

The invention therefore also relates to a process for the preparation ofcompounds of the formula I:

A process for the preparation of compounds of the formula I in which Vdenotes hydrogen or fluorine is characterised in that it comprises aprocess step in which a 2-substituted thiophene of the formula IIa orIIb

or a corresponding boronate containing the end group —B(OH)₃ ⁻ or—B(OH)₃M,in which M denotes a monovalent ionic radical as counterion to theboronate (in particular an alkali metal ion, such as Na⁺, K⁺, etc.),or

in which R¹, A¹, Z¹, V and a are as defined in claim 1, and

-   R³, R⁴ denote alkyl having 1-12 C atoms or R³+R⁴ together also    denote C₁-C₆-alkylene, in particular of the formula    —CH₂—(CH₂)_(p)—CH₂— or —C(CH₃)₂C(CH₃)₂—,    -   or 1,2-phenylene,    -   where R³, R⁴ and R³+R⁴ may also be substituted, in particular by        C₁-C₆-alkyl, F, Cl, C₁-C₆-alkoxy, and where p is 0 or 1,        is reacted with a compound of the formula III        Hal-(Z²-A²)_(b)-CF₂O-(A³-Z³)_(c)-A⁴-R²  III        in which Z², Z³, A², A³, A⁴, b, c and R² are as defined in claim        1, and        Hal denotes OSO₂CF₃, Cl, Br or I,        in the presence of a transition-metal catalyst, preferably a        palladium complex. The complexes are preferably palladium(II)        complexes, in particular bis(triphenylphosphine)palladium(II)        chloride. Hal preferably denotes chlorine or bromine, in        particular bromine. In formula III, b preferably denotes 1 or 2        and Z² preferably denotes a single bond. The radical Hal is        preferably bonded directly to a radical A². A² preferably        denotes an aromatic ring system. Preference is furthermore given        to the sub-forms indicated for the compounds of the formula I.

Further preferred process variants are revealed by the examples, thedetails of which—also generalised in accordance with general expertknowledge—are representative of preferred embodiments of the processaccording to the invention and the products thereof.

The invention also relates to liquid-crystalline media comprising one ormore of the compounds of the formula I according to the invention. Theliquid-crystalline media comprise at least two components, preferablyone or more compounds of the formula I and at least one furthercompound, which is preferably mesogenic. The media according to theinvention are preferably obtained by mixing the components with oneanother. A process according to the invention for the preparation of aliquid-crystalline medium is therefore characterised in that at leastone compound of the formula I is mixed with at least one furthermesogenic compound, and additives are optionally added.

The achievable combinations of clearing point, viscosity at lowtemperature, thermal/UV stability and high dielectric and opticalanisotropy are superior to previous materials from the prior art. At thesame time, low threshold voltages, good VHR values (VHR: ‘voltageholding ratio’) and good low-temperature stability are achieved.

Besides one or more compounds according to the invention, theliquid-crystalline media according to the invention preferably comprise,as further constituents, 2 to 40, particularly preferably 4 to 30,components. In particular, these media comprise 7 to 25 componentsbesides one or more compounds according to the invention.

The liquid-crystal media according to the invention are prepared in amanner conventional per se. In general, the desired amount of thecomponents used in lesser amount is dissolved in the components makingup the principal constituent, preferably at elevated temperature. It isalso possible to mix solutions of the components in an organic solvent,for example in acetone, chloroform or methanol, and to remove thesolvent again, for example by distillation, after thorough mixing. It isfurthermore possible to prepare the mixtures in other conventionalmanners, for example through the use of pre-mixes, for example homologuemixtures, or using so-called “multibottle” systems.

The dielectrics may also comprise further additives known to the personskilled in the art and described in the literature. For example, 0 to15%, preferably 0 to 10%, of pleochroic dyes, chiral dopants,stabilisers or nanoparticles may be added. The individual compoundsadded are employed in concentrations of 0.01 to 6%, preferably 0.1 to3%. However, the concentration data for the remaining constituents ofthe liquid-crystal mixtures, i.e. the liquid-crystalline or mesogeniccompounds, are indicated without taking into account the concentrationof these additives. The liquid-crystal media according to the inventionenable a significant broadening of the available parameter latitude.

The invention also relates to electro-optical displays (in particularTFT displays having two plane-parallel outer plates, which, togetherwith a frame, form one or more cells, integrated non-linear elements forswitching individual pixels on the outer plates, and a nematicliquid-crystal mixture having positive dielectric anisotropy and highspecific resistance which is located in the cell), which contain mediaof this type, and to the use of these media for electro-opticalpurposes.

The total amount of compounds of the formula I in the mixtures accordingto the invention is not crucial. The mixtures can therefore comprise oneor more further components for the purposes of optimisation of variousproperties. However, the observed effect on the addressing times and thethreshold voltage is generally greater, the higher the totalconcentration of compounds of the formula I.

Particularly preferred LC media according to the invention are mentionedbelow:

-   -   LC medium which additionally comprises one or more compounds of        the formulae II and/or III:

-   -   in which    -   ring A denotes 1,4-phenylene or trans-1,4-cyclohexylene,    -   a is 0 or 1,    -   R³ in each case, independently of one another, denotes alkyl        having 1 to 9 C atoms or alkenyl having 2 to 9 C atoms,        preferably alkenyl having 2 to 9 C atoms, and    -   R⁴ in each case, independently of one another, denotes an        unsubstituted or halogenated alkyl radical having 1 to 12 C        atoms, where, in addition, one or two non-adjacent CH₂ groups        may be replaced by —O—, —CH═CH—, —CH═CF—, —(CO)—, —O(CO)— or        —(CO)O— in such a way that O atoms are not linked directly to        one another, and preferably denotes alkyl having 1 to 12 C atoms        or alkenyl having 2 to 9 C atoms.    -   The compounds of the formula II are preferably selected from the        group consisting of the following formulae:

-   -   in which R^(3a) and R^(4a) each, independently of one another,        denote H, CH₃, C₂H₅ or C₃H₇, and “alkyl” denotes a        straight-chain alkyl group having 1 to 8, preferably 1, 2, 3, 4        or 5, C atoms. Particular preference is given to compounds of        the formulae IIa and IIf, in particular those in which R^(3a)        denotes H or CH₃, preferably H, and compounds of the formula        IIc, in particular those in which R^(3a) and R^(4a) denote H,        CH₃ or C₂H₅.    -   The compounds of the formula III are preferably selected from        the group consisting of the following formulae:

-   -   in which “alkyl” and R^(3a) have the meanings indicated above,        and R^(3a) preferably denotes H or CH₃. Particular preference is        given to compounds of the formula IIIb;    -   LC medium which additionally comprises one or more compounds        selected from the group consisting of the following formulae:

-   -   in which    -   R⁰ denotes an alkyl or alkoxy radical having 1 to 15 C atoms,        where, in addition, one or more CH₂ groups in these radicals may        each be replaced, independently of one another, by —C≡C—,        —CF₂O—, —CH═CH—,

—O—, —(CO)O— or —O(CO)—in such a way that O atoms are not linkeddirectly to one another, and in which, in addition, one or more H atomsmay be replaced by halogen,

-   -   X⁰ denotes F, Cl, CN, SF₅, SCN, NCS, a halogenated alkyl        radical, halogenated alkenyl radical, halogenated alkoxy radical        or halogenated alkenyloxy radical, each having up to 6 C atoms,    -   Y¹⁻⁶ each, independently of one another, denote H or F,    -   Z⁰ denotes —C₂H₄—, —(CH₂)₄—, —CH═CH—, —CF═CF—, —C₂F₄—, —CH₂CF₂—,        —CF₂CH₂—, —CH₂O—, —OCH₂—, —COO—, —CF₂O— or —OCF₂—, in the        formulae V and VI also a single bond, and    -   b and c each, independently of one another, denote 0 or 1.    -   In the compounds of the formulae IV to VIII, X⁰ preferably        denotes F or OCF₃, furthermore OCHF₂, CF₃, CF₂H, Cl, OCH═CF₂. R⁰        is preferably straight-chain alkyl or alkenyl, each having up to        6 C atoms.    -   The compounds of the formula IV are preferably selected from the        group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above.    -   Preferably, R⁰ in formula IV denotes alkyl having 1 to 8 C atoms        and X⁰ denotes F, Cl, OCHF₂ or OCF₃, furthermore OCH═CF₂. In the        compound of the formula IVb, R⁰ preferably denotes alkyl or        alkenyl. In the compound of the formula IVd, X⁰ preferably        denotes Cl, furthermore F.    -   The compounds of the formula V are preferably selected from the        group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above.        Preferably, R⁰ in formula V denotes alkyl having 1 to 8 C atoms        and X⁰ denotes F;    -   LC medium which comprises one or more compounds of the formula        VI-1:

-   -   particularly preferably those selected from the group consisting        of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above.        Preferably, R⁰ in formula VI denotes alkyl having 1 to 8 C atoms        and X⁰ denotes F, furthermore OCF₃.    -   LC medium which comprises one or more compounds of the formula        VI-2:

-   -   particularly preferably those selected from the group consisting        of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above.    -   Preferably, R⁰ in formula VI denotes alkyl having 1 to 8 C atoms        and X⁰ denotes F;    -   LC medium which preferably comprises one or more compounds of        the formula VII in which Z⁰ denotes —CF₂O—, —CH₂CH₂— or —(CO)O—,        particularly preferably those selected from the group consisting        of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above.        Preferably, R⁰ in formula VII denotes alkyl having 1 to 8 C        atoms and X⁰ denotes F, furthermore OCF₃.    -   The compounds of the formula VIII are preferably selected from        the group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above. R⁰        preferably denotes a straight-chain alkyl radical having 1 to 8        C atoms. X⁰ preferably denotes F.    -   LC medium which additionally comprises one or more compounds of        the following formula:

-   -   -   in which R⁰, X⁰, Y¹ and Y² have the meaning indicated above,            and

each, independently of one another, denote

where the rings A and B do not both simultaneously denote cyclohexylene.

-   -   The compounds of the formula IX are preferably selected from the        group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above.        Preferably, R⁰ denotes alkyl having 1 to 8 C atoms and X⁰        denotes F. Particular preference is given to compounds of the        formula IXa;    -   LC medium which additionally comprises one or more compounds        selected from the group consisting of the following formulae:

-   -   in which R⁰, X⁰ and Y¹⁻⁴ have the meanings indicated above, and

each, independently of one another, denote

-   -   The compounds of the formulae X and XI are preferably selected        from the group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above.        Preferably, R⁰ denotes alkyl having 1 to 8 C atoms and/or X⁰        denotes F. Particularly preferred compounds are those in which        Y¹ denotes F and Y² denotes H or F, preferably F;    -   LC medium which additionally comprises one or more compounds of        the following formula XII:

-   -   in which R⁵ and R⁶ each, independently of one another, denote        n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having        up to 9 C atoms, and preferably each, independently of one        another, denote alkyl having 1 to 7 C atoms or alkenyl having 2        to 7 C atoms. Y¹ denotes H or F.    -   Preferred compounds of the formula XII are those selected from        the group consisting of the following formulae:

-   -   in which    -   alkyl and alkyl* each, independently of one another, denote a        straight-chain alkyl radical having 1 to 6 C atoms, and    -   alkenyl and alkenyl* each, independently of one another, denote        a straight-chain alkenyl radical having 2 to 6 C atoms.    -   Very particular preference is given to compounds of the        following formula:

-   -   in which alkyl has the meaning indicated above and R^(6a)        denotes H or CH₃.    -   LC medium which additionally comprises one or more compounds        selected from the group consisting of the following formulae:

-   -   in which R⁰, X⁰, Y¹ and Y² have the meanings indicated above.        Preferably, R⁰ denotes alkyl having 1 to 8 C atoms and X⁰        denotes F or Cl.    -   The compounds of the formulae XIII and XIV are preferably        selected from the group consisting of the following formulae:

-   -   in which R⁰ and X⁰ have the meanings indicated above. R⁰        preferably denotes alkyl having 1 to 8 C atoms. In the compounds        of the formula XIII, X⁰ preferably denotes F or Cl.    -   LC medium which additionally comprises one or more compounds of        the formulae D1 and/or D2:

-   -   in which Y¹, Y², R⁰ and X⁰ have the meaning indicated above.        Preferably, R⁰ denotes alkyl having 1 to 8 C atoms and X⁰        denotes F. Particular preference is given to compounds of the        following formulae:

-   -   in which R⁰ has the meanings indicated above and preferably        denotes straight-chain alkyl having 1 to 6 C atoms, in        particular C₂H₅, n-C₃H₇ or n-C₅H₁₁.    -   LC medium which additionally comprises one or more compounds of        the following formulae:

-   -   in which Y¹, R¹ and R² have the meaning indicated above. R¹ and        R² preferably each, independently of one another, denote alkyl        having 1 to 8 C atoms. Y¹ preferably denotes F. Preferred media        comprise 1-15% by weight, in particular 1-10% by weight, of        these compounds.    -   LC medium which additionally comprises one or more compounds of        the following formula:

-   -   in which X⁰, Y¹ and Y² have the meanings indicated above, and        “alkenyl” denotes C₂₋₇-alkenyl. Particular preference is given        to compounds of the following formula:

-   -   in which R^(3a) has the meaning indicated above and preferably        denotes H;    -   LC medium which additionally comprises one or more tetracyclic        compounds selected from the group consisting of the formulae XIX        to XXV:

-   -   in which Y¹⁻⁴, R⁰ and X⁰ each, independently of one another,        have one of the meanings indicated above. X⁰ is preferably F,        Cl, CF₃, OCF₃ or OCHF₂. R⁰ preferably denotes alkyl, alkoxy,        oxaalkyl, fluoroalkyl or alkenyl, each having up to 8 C atoms.    -   LC medium which additionally comprises one or more compounds of        the following formula:

-   -   in which R⁰, X⁰ and Y″ have the meanings indicated above.        Particular preference is given to compounds of the following        formula:

-   -   LC medium which additionally comprises one or more compounds of        the following formula:

-   -   in which R⁰, Y¹, Y² and X⁰ are as defined above. R⁰ particularly        preferably denotes an n-butyl radical.

is preferably

-   -   R⁰ is generally preferably straight-chain alkyl or alkenyl        having 2 to 7 C atoms;    -   X⁰ is preferably F, furthermore OCF₃, Cl or CF₃;    -   the medium preferably comprises one, two or three compounds of        the formula I;    -   the medium preferably comprises in each case one or more        compounds selected from the group of the compounds of the        formulae I and II;    -   the medium preferably comprises one or more compounds selected        from the group of the compounds of the formulae VI-2, VII-1a,        VII-1b, IX, X, XI and XXV (CF₂O-bridged compounds); the total        content of compounds of the formulae VI-2, VII-1a, VII-1b, IX,        X, XI and XXV and of the compounds of the formula I according to        the invention is preferably 35% by weight or more, particularly        preferably 40% by weight or more and very particularly        preferably 45% by weight or more;    -   the medium preferably comprises 1-25% by weight, preferably        10-20% by weight, of compounds of the formula I;    -   the proportion of compounds of the formulae II-XXVII in the        mixture as a whole is preferably 20 to 99% by weight;    -   the medium preferably comprises 25-80% by weight, particularly        preferably 30-70% by weight, of compounds of the formulae II        and/or III;    -   the medium preferably comprises 20-70% by weight, particularly        preferably 25-60% by weight, of compounds of the formula IIa;    -   the medium preferably comprises 2-25% by weight, particularly        preferably 3-20% by weight, of compounds selected from the group        of the compounds of the formulae I and VI-2; in a particularly        preferred embodiment, a small proportion or no compound of the        formula VI-2 is present. The compound of the formula I then        completely or partly replaces this component;    -   the medium comprises in total 2-30% by weight, particularly        preferably 3-20% by weight, of compounds of the formulae XI and        XXVI together;    -   the medium preferably comprises 1-20% by weight, particularly        preferably 2-15% by weight, of compounds of the formula XXIV;    -   the medium comprises in total 15-65% by weight, particularly        preferably 30-55% by weight, of compounds selected from the        highly polar compounds of the formulae VI-2, X, XI and XXVII        together.

It has been found that even a relatively small proportion of compoundsof the formula I mixed with conventional liquid-crystal materials, butin particular with one or more compounds of the formulae II to XXIX,results in a significant increase in the dielectric anisotropy and inlow rotational viscosity values, with broad nematic phases having lowsmectic-nematic transition temperatures being observed at the same time,improving the storage stability. The media simultaneously exhibit verylow threshold voltages and very good values for the VHR on exposure toUV.

The term “alkyl” encompasses straight-chain and branched alkyl groupshaving 1-9 carbon atoms, in particular the straight-chain groups methyl,ethyl, propyl, butyl, pentyl, hexyl and heptyl. Groups having 2-5 carbonatoms are generally preferred.

The term “alkenyl” encompasses straight-chain and branched alkenylgroups having up to 9 carbon atoms, in particular the straight-chaingroups. Particularly preferred alkenyl groups are C₂-C₇-1 E-alkenyl,C₄-C₇-3E-alkenyl, C₅-C₇-4-alkenyl, C₆-C₇-5-alkenyl and C₇-6-alkenyl, inparticular C₂-C₇-1 E-alkenyl, C₄-C₇-3E-alkenyl and C₅-C₇-4-alkenyl.Examples of preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl,1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl,3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl,4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups having up to 5carbon atoms are generally preferred.

The term “fluoroalkyl” in this application encompasses straight-chaingroups containing at least one fluorine atom, preferably a terminalfluorine, i.e. fluoromethyl, 2-fluoroethyl, 3-fluoropropyl,4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and 7-fluoroheptyl.However, other positions of the fluorine are not excluded.

The term “halogenated alkyl radical” preferably encompasses mono- orpolyfluorinated and/or -chlorinated radicals. Perhalogenated radicalsare included. Particular preference is given to fluorinated alkylradicals, in particular CF₃, CH₂CF₃, CH₂CHF₂, CHF₂, CH₂F, CHFCF₃ andCF₂CHFCF₃.

The term “alkylene” encompasses straight-chain or branched alkanediylgroups having 1-12 carbon atoms, in particular the straight-chain groupsmethylene, ethylene, propylene, butylene and pentylene. Groups having2-8 carbon atoms are generally preferred.

The term “oxaalkyl” or “alkoxy” in this application encompassesstraight-chain radicals of the formula C_(n)H_(2n+1)—O—(CH₂)_(m), inwhich n and m each, independently of one another, denote 1 to 6. m mayalso denote 0. Preferably, n=1 and m=1-6 or m=0 and n=1-3.

If R⁰ in the formulae above and below denotes an alkyl radical and/or analkoxy radical, this may be straight-chain or branched. It is preferablystraight-chain, has 2, 3, 4, 5, 6 or 7 C atoms and accordinglypreferably denotes ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy,propoxy, butoxy, pentoxy, hexyloxy or heptyloxy, furthermore methyl,octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy ortetradecoxy.

Oxaalkyl preferably denotes straight-chain 2-oxapropyl (=methoxymethyl),2-(=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-, 3- or4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl,2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl,2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxa-decyl.

If R⁰ denotes an alkyl radical in which a CH₂ group has been replaced by—CH═CH—, this may be straight-chain or branched. It is preferablystraight-chain and has 2 to 10 C atoms. Accordingly, it denotes, inparticular, vinyl, prop-1- or -2-enyl, but-1-, -2- or -3-enyl, pent-1-,-2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, -2-,-3-, -4-, -5- or -6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6- or -7-enyl,non-1-, -2-, -3-, -4-, -5-, -6-, -7- or -8-enyl, dec-1-, -2-, -3-, -4-,-5-, -6-, -7-, -8- or -9-enyl. These radicals may also be mono- orpolyhalogenated.

If R⁰ denotes an alkyl or alkenyl radical which is at leastmonosubstituted by halogen, this radical is preferably straight-chainand halogen is preferably F or Cl. In the case of polysubstitution,halogen is preferably F. The resultant radicals also includeperfluorinated radicals. In the case of monosubstitution, the fluorineor chlorine substituent may be in any desired position, but ispreferably in the ω-position.

In the formulae above and below, X⁰ is preferably F, Cl or a mono- orpolyfluorinated alkyl or alkoxy radical having 1, 2 or 3 C atoms or amono- or polyfluorinated alkenyl radical having 2 or 3 C atoms. X⁰ isparticularly preferably F, Cl, CF₃, CHF₂, OCF₃, OCHF₂, OCFHCF₃,OCFHCHF₂, OCFHCH₂F, OCF₂CH₃, OCF₂CHF₂, OCF₂CH₂F, OCF₂CF₂CHF₂,OCF₂CF₂CH₂F, OCFHCF₂CF₃, OCFHCF₂CHF₂, OCH═CF₂, OCF═CF₂, OCF₂CHFCF₃,OCF₂CF₂CF₃, OCF₂CF₂CCIF₂, OCCIFCF₂CF₃, CF═CF₂, CF═CHF or CH═CF₂, veryparticularly preferably F or OCF₃.

Through a suitable choice of the meanings of R⁰ and X⁰, the addressingtimes, the threshold voltage, the steepness of the transmissioncharacteristic lines, etc., can be modified in the desired manner. Forexample, 1E-alkenyl radicals, 3E-alkenyl radicals, 2E-alkenyloxyradicals and the like generally result in shorter addressing times,improved nematic tendencies and a higher ratio between the elasticconstants k₃₃ (bend) and k₁₁ (splay) compared with alkyl and alkoxyradicals. 4-Alkenyl radicals, 3-alkenyl radicals and the like generallygive lower threshold voltages and lower values of k₃₃/k₁₁ compared withalkyl and alkoxy radicals. The media according to the invention aredistinguished, in particular, by high K₁ values and thus havesignificantly faster response times than the media from the prior art.

The optimum mixing ratio of the compounds of the above-mentionedformulae depends substantially on the desired properties, on the choiceof the components of the above-mentioned formulae and on the choice ofany further components that may be present.

Suitable mixing ratios within the range indicated above can easily bedetermined from case to case.

In a preferred embodiment of the media according to the invention, thedielectric anisotropy is 13 or more, preferably 17 or more. The opticalanisotropy here is preferably between 0.10 or more and 0.14 or less,particularly preferably between 0.11 and 0.13. The clearing point hereis preferably between 70° C. or more and 120° C. or less. The mixture ispreferably stable down to −25° C. Media of this type have a very lowthreshold voltage. Media of this type preferably comprise 55% by weightor more of highly polar compounds having a dielectric anisotropy of 10or more. They particularly preferably comprise 45% by weight or more ofhighly polar compounds having a dielectric anisotropy of 20 or more.Compounds of this type are generally selected from compounds of theformulae I, VI-2, X, XI and XXVII. Suitable individual compounds aregiven by comparison of the formulae I, VI-2, X, XI and XXVII with theexamples.

In a further preferred embodiment of the media according to theinvention, the rotational viscosity is 90 mPas or less, preferably 80mPas or less. The optical anisotropy here is preferably between 0.08 ormore and 0.14 or less, particularly preferably between 0.11 and 0.13.The clearing point here is preferably between 70° C. or more and 100° C.or less. Media of this type generally have a relatively fast responsetime. The proportion of compounds of the formula II is preferably 40% byweight or more, particularly preferably 45% by weight or more. In thecase where no compounds of the formula II in which a=1 are employed, theproportion of compounds of the formula II in which a=0 iscorrespondingly increased. The proportion of non-polar compounds of theformulae IIa and IIb together is, in accordance with this embodiment,preferably greater than 30% by weight, particularly preferably 35% byweight or more. Accordingly, the proportion of compounds of the formulaII in which a=1 can preferably be varied between 0 and 25% by weight orless.

The total amount of compounds of the above-mentioned formulae in themixtures according to the invention is not crucial. The mixtures cantherefore comprise one or more further components for the purposes ofoptimisation of various properties. However, the observed effect on thedesired improvement in the properties of the mixture is generallygreater, the higher the total concentration of compounds of theabove-mentioned formulae.

The individual compounds of the above-mentioned formulae and thesubformulae thereof which can be used in the media according to theinvention are either known or methods for their preparation can readilybe derived from the prior art by the person skilled in the relevant artsince they are based on standard methods described in the literature.

The liquid-crystal media according to the invention enable a significantbroadening of the available parameter latitude.

The media according to the invention are particularly suitable formobile applications and high-Δn TFT applications, such as, for example,PDAs, notebooks, LCD TVs and monitors.

The liquid-crystal media according to the invention, with retention ofthe nematic phase down to −20° C. and preferably down to −30° C.,particularly preferably down to −40° C., and of the clearing point ≧70°C., preferably ≧75° C., simultaneously enable rotational viscosities γ₁of ≦110 mPa·s, particularly preferably ≦90 mPa·s, to be achieved,enabling excellent MLC displays having fast response times to beobtained.

The dielectric anisotropy Δ∈ of the liquid-crystal media according tothe invention is preferably ≧+5, particularly preferably ≧+10. Inaddition, the media are characterised by low operating voltages. Thethreshold voltage of the liquid-crystal media according to the inventionis preferably ≦1.4 V, in particular ≦1.2 V, in media adapted for thepurpose also ≦1.0 V.

The birefringence Δn of the liquid-crystal media according to theinvention is preferably ≧0.10, particularly preferably ≧0.11. Δn ispreferably ≦0.15, particularly preferably ≦0.13

Further particularly preferred embodiments of the invention extend tothe following parameters:

The nematic phase range of the liquid-crystal media according to theinvention preferably has a width of at least 90°, in particular at least100°. This range preferably extends at least from −25° C. or less to+70° C. or more, particularly preferably from −30 to 80° C. or higher.In a further preferred embodiment, the clearing point is between 70 and100° C., particularly preferably between 75 and 90° C.

It goes without saying that, through a suitable choice of the componentsof the media according to the invention, it is also possible for higherclearing points (for example above 100° C.) to be achieved at higherthreshold voltages or lower clearing points to be achieved at lowerthreshold voltages with retention of the other advantageous properties.At viscosities correspondingly increased only slightly, it is likewisepossible to obtain media having a higher Δ∈ and thus low thresholds. TheMLC displays according to the invention preferably operate at the firstGooch and Tarry transmission minimum [C. H. Gooch and H. A. Tarry,Electron. Lett. 10, 2-4, 1974; C. H. Gooch and H. A. Tarry, Appl. Phys.,Vol. 8, 1575-1584, 1975], where, besides particularly favourableelectro-optical properties, such as, for example, high steepness of thecharacteristic line and low angle dependence of the contrast (Germanpatent 30 22 818), lower dielectric anisotropy is sufficient at the samethreshold voltage as in an analogous display at the second minimum. Thisenables significantly higher specific resistance values to be achievedusing the media according to the invention at the first minimum than inthe case of media comprising cyano compounds. Through a suitable choiceof the individual components and their proportions by weight, the personskilled in the art is able to set the birefringence necessary for apre-specified layer thickness of the MLC display using simple routinemethods.

Measurements of the voltage holding ratio (HR) [S. Matsumoto et al.,Liquid Crystals 5, 1320 (1989); K. Niwa et al., Proc. SID Conference,San Francisco, June 1984, p. 304 (1984); G. Weber et al., LiquidCrystals 5, 1381 (1989)] have shown that media according to theinvention comprising compounds of the formula I exhibit a significantlysmaller decrease in the HR on UV exposure than analogous mediacomprising cyanophenylcyclohexanes of the formula

or esters of the formula

The LC media are preferably 99% by weight, particularly preferably 100%by weight, free from benzonitrile derivatives.

The LC media may also comprise further additives known to the personskilled in the art and described in the literature, such as, forexample, UV stabilisers, such as Tinuvin® from Ciba, antioxidants,free-radical scavengers, nanoparticles, etc. For example, 0-15% ofpleochroic dyes or chiral dopants can be added. Suitable dopants arementioned below in Table C.

The LC media preferably comprise 0 to 10% by weight, in particular 0.01to 5% by weight and particularly preferably 0.1 to 3% by weight, ofstabilisers. The LC media preferably comprise one or more stabilisersselected from 2,6-di-tert-butylphenols, 2,2,6,6-tetramethylpiperidinesand 2-benzotriazol-2-ylphenols. These assistants are known to the personskilled in the art and are commercially available, for example aslight-protection agents.

The following examples explain the invention without intending to limitit. Above and below, percentage data denote percent by weight. Alltemperatures are indicated in degrees Celsius. Furthermore, Tg denotesglass transition temperature, C=crystalline state, N=nematic phase,Sm=smectic phase and I=isotropic phase. The data between these symbolsrepresent the transition temperatures. Δn denotes optical anisotropy(589 nm, 20° C.), Δ∈ the dielectric anisotropy (1 kHz, 20° C.), and γ₁the rotational viscosity (in the unit mPa·s).

The substituents on the saturated 1,4-substituted ring systems drawn inthe synthesis examples are, unless indicated otherwise, in the transconfiguration. The other formulae stand for both configurations andpreferably for the trans configuration

In the present application and in the examples below, the structures ofthe liquid-crystal compounds are indicated by means of acronyms, withthe transformation into chemical formulae taking place in accordancewith Tables A and B below. All radicals C_(n)H_(2n+1) and C_(m)H_(2m+1)are straight-chain alkyl radicals having n and m C atoms respectively;n, m and k are integers and preferably denote 0, 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 11 or 12. The coding in Table B is self-evident. In Table A, onlythe acronym for the parent structure is indicated. In individual cases,the acronym for the parent structure is followed, separated by a dash,by a code for the substituents R¹⁺, R²⁺, L¹⁺ and L²⁺:

Code for R¹*, R²*, L¹*, L²*, L³* R¹* R²* L¹* L²* nm C_(n)H_(2n+1)C_(m)H_(2m+1) H H nOm C_(n)H_(2n+1) OC_(m)H_(2m+1) H H nO.mOC_(n)H_(2n+1) C_(m)H_(2m+1) H H n C_(n)H_(2n+1) CN H H nN.FC_(n)H_(2n+1) CN F H nN.F.F C_(n)H_(2n+1) CN F F nF C_(n)H_(2n+1) F H HnCl C_(n)H_(2n+1) Cl H H nOF OC_(n)H_(2n+1) F H H nF.F C_(n)H_(2n+1) F FH nF.F.F C_(n)H_(2n+1) F F F nOCF₃ C_(n)H_(2n+1) OCF₃ H H nOCF₃.FC_(n)H_(2n+1) OCF₃ F H n-Vm C_(n)H_(2n+1) —CH═CH—C_(m)H_(2m+1) H H nV-VmC_(n)H_(2n+1)—CH═CH— —CH═CH—C_(m)H_(2m+1) H H

Preferred mixture components are found in Tables A and B.

TABLE A

  PYP

  BCH

  CCH

  CPTP

  PYRP

  CBC

  CCP

  CEPTP

  ECCP

  EPCH

  CH

  PTP

  CP

  EBCH

  B

  CECP

  PCH

  CCPC

  BECH

  CPC

  FET-nF

  CGG

  CFU

  CGU

TABLE B

  APU-n-OXF

  APUQU-n-F

  BCH-n•Fm

  CBC-nmF

  ECCP-nm

  ACQU-n-F

  CFU-n-F

  CCZU-n-F

  PGP-n-m

  CDUQU-n-F

  CDU-n-F

  CGG-n-F

  CC-nV-Vm

  CCP-Vn-m

  CCP-nV-m

  CCQU-n-F

  CGU-n-F

  DCU-n-F

  CPZG-n-OT

  CCG-V-F

  CC-n-V

  CC-n-Vm

  CPPC-nV-Vm

  CCQG-n-F

  Dec-U-n-F

  CPGP-n-m

  CWCG-n-F

  CCOC-n-m

  CPTU-n-F

  CQU-n-F

  CWCU-n-F

  GPTU-n-F

  PQU-n-F

  PGU-n-F

  CCGU-n-F

  DPGU-n-F

  CUQU-n-F

  CCCQU-n-F

  CGUQU-n-F

  PUQU-n-F

  CGZP-n-OT

  CCQG-n-F

  DPGU-n-OT

  CPGU-n-OT

  PYP-n-F

  CPGU-n-F

  CVCP-1V-OT

  PP-nV-Vm

  CWCQU-n-F

  PPGU-n-F

  CPU-n-OXF

  CPGG-n-F

  GGP-n-Cl

  PP-1-nVm

  PGUQU-n-F

  GPQU-n-F

  PGP-n-kVm

  PP-n-kVm

  PCH-nCl

  GGP-n-F

  SUQU-n-F

  SPUQU-n-F

  MPP-n-F

  GP-n-Cl

  PGIGI-n-F

In a preferred embodiment of the present invention, the LC mediaaccording to the invention comprise one or more compounds selected fromthe group consisting of compounds from Tables A and B.

TABLE C TABLE C indicates possible dopants which can be added to the LCmedia according to the invention

  C 15

  CM 21

  CM 44

  CM 47

  R/S-2011

  CB 15

  R/S-811

  CM 45

  CN

  R/S-3011

  R/S-4011

  R/S-1011

  R/S-5011

The LC media preferably comprise 0 to 10% by weight, in particular 0.01to 5% by weight and particularly preferably 0.1 to 3% by weight, ofdopants. The LC media preferably comprise one or more dopants selectedfrom the group consisting of compounds from Table C.

Physical, physicochemical and electro-optical parameters are determinedby generally known methods, as described, inter alia, in the brochure“Merck Liquid Crystals—Licristal®—Physical Properties of LiquidCrystals—Description of the Measurement Methods”, 1998, Merck KGaA,Darmstadt. The dielectric anisotropy Δ∈ of individual substances isdetermined at 20° C. and 1 kHz. To this end, 5-10% by weight of thesubstance to be investigated is measured dissolved in the dielectricallypositive mixture ZLI-4792 (Merck KGaA), and the measurement value isextrapolated to a concentration of 100%. The optical anisotropy Δn isdetermined at 20° C. and a wavelength of 589.3 nm, and the rotationalviscosity γ₁ is determined at 20° C., both likewise by linearextrapolation. The clearing point is determined on the pure substanceor, if that is not possible, likewise by extrapolation from ZLI-4792.

In addition, the following abbreviations and symbols are used:

-   V₀ threshold voltage, capacitive [V] at 20° C.,-   V₁₀ optical threshold for 10% relative contrast [V] at 20° C.,-   n_(e) extraordinary refractive index at 20° C. and 589 nm,-   n_(o) ordinary refractive index at 20° C. and 589 nm,-   Δn optical anisotropy at 20° C. and 589 nm,-   ∈_(⊥) dielectric susceptibility perpendicular to the director at    20° C. and 1 kHz,-   ∈_(∥) dielectric susceptibility parallel to the director at 20° C.    and 1 kHz,-   Δ∈ dielectric anisotropy at 20° C. and 1 kHz,-   cl.p., T(N,I) clearing point [° C.],-   γ₁ rotational viscosity at 20° C. [mPa·s],-   K₁ elastic constant, “splay” deformation at 20° C. [pN],-   K₂ elastic constant, “twist” deformation at 20° C. [pN],-   K₃ elastic constant, “bend” deformation at 20° C. [pN],-   LTS low-temperature stability (phase), determined in test cells or    on a stock quantity (bulk).

Unless explicitly noted otherwise, all concentrations in the presentapplication are indicated in percent by weight and relate to thecorresponding mixture as a whole without solvents.

The term “threshold voltage” for the present invention relates to thecapacitive threshold (V₀), also called the Freedericks threshold, unlessexplicitly indicated otherwise. In the examples, as generally usual, theoptical threshold for 10% relative contrast (V₁₀) may also be indicated.

The test cells used for measurement of the capacitive threshold voltageV₀ and for V₁₀ are constructed from substrates consisting of soda-limeglass coated with polyimide alignment layers (Durimid 32 with diluent(70% of NMP+30% of xylene) in the ratio 1:4) from Arch Chemicals, whichare rubbed antiparallel to one another and have a surface tilt of quasi0 degrees. The area of the transparent, virtually square ITO electrodesis 1 cm². The capacitive threshold voltage is determined using astandard commercial high-resolution LCR meter (for example HewlettPackard 4284A LCR meter).

The following abbreviations are used:

-   LC liquid-crystal or liquid-crystalline-   THF tetrahydrofuran-   MTB ether methyl t-butyl ether

EXAMPLE 1

656 ml (15% solution in n-hexane) (1.04 mol) of butyllithium are addedto a solution of 116 g (950 mmol) of 2-ethylthiophene in 200 ml of THFat −70° C. under nitrogen. The batch is subsequently stirred at −70° C.for 30 min and at −20° C. for 20 min. 124 ml (1.09 mol) of trimethylborate are added to the mixture at −70° C., and the mixture is stirredat low temperature for 30 min. The cold bath is removed, and the batchis diluted with 500 ml of water at −15° C. and acidified usinghydrochloric acid. The aqueous phase is extracted with MTB ether, andthe combined organic phases are washed with sat. sodium chloridesolution, dried over sodium sulfate and evaporated. The residue isdissolved in 1000 ml of THF, and 80 ml of 50% sodium hydroxide solutionare added with stirring and cooling. The batch is cooled to −10° C., andthe precipitated solid is separated off.

30.9 g (112 mmol) of sodium metaborate octahydrate are initiallyintroduced in 45 ml of water and 125 ml of THF, and 1.1 g (1.5 mmol) ofbis(triphenylphosphine)palladium(II) chloride and 0.1 ml (1.5 mmol) ofhydrazinium hydroxide are added. After 5 min, 14.7 g (75 mmol) of theboronate 3 and 29.2 g (75 mmol) of the bromide 4 are added, and thebatch is heated at the boil for 8 h. The batch is subsequently dilutedwith MTB ether. The organic phase is evaporated, and the residue ispassed over silica gel (n-heptane). The further purification is carriedout by crystallisation from n-pentane (m.p. 36° C.).

C 36 I

Δn=0.128

Δ∈=24

γ₁=47 mP·s

The following compounds are prepared analogously:

C 22 I

Δn=0.126

Δ∈=24

γ₁=50 mPa·s

EXAMPLE 2

The intermediate 8 is prepared analogously to step 1.2.

The product 10 is prepared in accordance with the reaction conditionsfor step 1.2.

C 143 N (138) I

Δn=0.243

Δ∈=29

EXAMPLE 3

The bromine atom on the thiophene derivative 11 can be replaced by afluorine atom in accordance with Synth. Commun. 2008, 38 (1), 72-76 orEur. J. Org. Chem. 2005, 1, 91-97. The boronate is subsequently preparedanalogously to the procedure indicated above (step 1.1).

Substance 14 is prepared from the boronate of the formula 13 by themethod described under Example 1 (step 1.2).

EXAMPLE 4

Compound 15 is prepared analogously to Examples 2 and 3.

EXAMPLE 5

Compound 16 can be prepared by the relevant processes from the knownprecursors indicated (cf. general part).

C 68 I

Δn=0.098

Δ∈=17

γ₁=57 mP·s

The following compound is prepared analogously:

MIXTURE EXAMPLE M1

CC-3-V 32.5% S → N [° C.]: <−30.0 CCQU-3-F 7.0% Clearing point [° C.]:+81 SUQU-2-F 13.0% Δn [589 nm; 20° C.]: +0.127 PGU-3-F 2.0% Δε +21.8CCP-V-1 7.5% γ₁ [mPa · s; 20° C.]: 107 APUQU-3-F 8.0% PGUQU-3-F 5.0% V₁₀[V]: 0.97 PGUQU-4-F 8.0% V₉₀ [V]: 1.49 PGUQU-5-F 7.0% DPGU-4-F 10.0%100.0%

The mixture is highly suitable for TN-TFT.

MIXTURE EXAMPLE M2

CC-3-V 35.0% S → N [° C.]: <−40 SUQU-2-F 14.0% Clearing point [° C.]:80.5 PGU-3-F 5.0% Δn [589 nm; 20° C.]: 0.126 CCP-V-1 16.0% Δε +16.5PGUQU-3-F 5.0% γ₁ [mPa · s; 20° C.]: 89 PGUQU-4-F 7.0% PGUQU-5-F 8.0%V₁₀ [V]: 1.10 DPGU-4-F 10.0% V₉₀ [V]: 1.55 100.0%

The mixture is highly suitable for TN-TFT.

MIXTURE EXAMPLE M3

CC-3-V 29.5% S → N [° C.]: <−30 SUQU-2-F 15.0% Clearing point [° C.]:78.5 PGU-3-F 8.5% Δn [589 nm; 20° C.]: 0.130 PGP-2-2V 4.0% Δε +18CCP-V-1 14.0% γ₁ [mPa · s; 20° C.]: 95 APUQU-2-F 9.0% APUQU-3-F 10.0%V₁₀ [V]: 1.07 PGUQU-3-F 5.0% V₉₀ [V]: 1.62 CPGU-3-OT 5.0% 100.0%

The mixture is highly suitable for TN-TFT.

MIXTURE EXAMPLE M4

CC-3-V 30.0% S → N [° C.]: <−25 SUQU-2-F 15.0% Clearing point [° C.]:80.5 PGU-3-F 7.0% Δn [589 nm; 20° C.]: 0.129 PGP-2-2V 5.0% Δε +16.3CCP-V-1 15.5% γ₁ [mPa · s; 20° C.]: 92 APUQU-2-F 8.5% APUQU-3-F 9.0% V₁₀[V]: 1.11 PGUQU-3-F 5.0% V₉₀ [V]: 1.68 CPGU-3-OT 5.0% 100.0%

The mixture is highly suitable for TN-TFT.

MIXTURE EXAMPLE M5

CC-3-V 35.0% SUQU-2-F 12.5% CCP-V-1 15.0% PGUQU-3-F 4.0% CPGU-3-OT 5.0%APUQU-2-F 3.0% APUQU-3-F 10.0% PGP-2-2V 7.5% PGU-3-F 8.0% 100.0%

The mixture is highly suitable for TN-TFT.

MIXTURE EXAMPLE M6

CC-3-V 40.0% CCGU-3-F 6.0% Clearing point [° C.]: 75 PGUQU-3-F 5.0% Δn[589 nm; 20° C.]: 0.103 APUQU-2-F 3.0% Δε +14.3 APUQU-3-F 11.0% γ₁ [mPa· s; 20° C.]: 79 CPGU-3-OT 3.0% CCQU-3-F 10.0% V₀ [V]: 0.92 CCQU-5-F7.0% PGU-2-F 5.0% SUQU-2-F 10.0% 100.0%

The mixture is highly suitable for IPS.

MIXTURE EXAMPLE M7

SUQU-2-F 14.0% CCGU-3-F 3.0% Clearing point [° C.]: 88 CC-3-V 32.0% Δn[589 nm; 20° C.]: 0.124 CCP-V-1 10.0% Δε +11.3 CCP-V2-1 11.0% γ₁ [mPa ·s; 20° C.]: 86 PGP-2-3 5.0% PGP-2-4 5.0% V₀ [V]: 1.16 APUQU-2-F 2.0% LTS(bulk, −30° C.): >500 h APUQU-3-F 11.0% PGUQU-3-F 7.0% 100.0%

The mixture is highly suitable for IPS.

MIXTURE EXAMPLE M8

PGUQU-3-F 7.5% CPGU-3-OT 3.5% Clearing point [° C.]: 74.5 SUQU-2-F 9.0%Δn [589 nm; 20° C.]: 0.131 PP-1-2V1 1.5% Δε +7.4 CC-3-V 44.0% γ₁ [mPa ·s; 20° C.]: 56 PGP-2-2V 18.0% CPU-3-OXF 16.5% V₁₀ [V]: 1.55 100.0% V₉₀[V]: 2.30

The mixture is highly suitable for TN-TFT.

MIXTURE EXAMPLE M9

CC-3-V 40.5% APUQU-2-F 4.0% Clearing point [° C.]: 75 APUQU-3-F 8.5% Δn[589 nm; 20° C.]: 0.126 CPGU-3-OT 2.0% Δε +12.0 PGUQU-3-F 9.0% γ₁ [mPa ·s; 20° C.]: 71 SUQU-3-F 8.0% PGP-2-2V 9.0% V₁₀ [V]: 1.21 CPU-3-OXF 19.0%V₉₀ [V]: 1.83 100.0%

The mixture is highly suitable for TN-TFT.

Further combinations of the embodiments and variants of the invention inaccordance with the description also arise from the following claims.

The invention claimed is:
 1. A liquid crystalline-medium comprising oneor more compounds of formula I

in which R¹ and R² each, independently of one another, denote H, ahalogenated or unsubstituted alkyl radical having 1 to 15 C atoms,where, in addition, one or more CH₂ groups in these radicals may each bereplaced, independently of one another, by —C≡C—, —CH═CH—, —(CO)O—,—O(CO)—, —(CO)— or —O— in such a way that O atoms are not linkeddirectly to one another, where R² additionally denotes F, Cl, Br, CN,SCN, NCS or SF₅, A¹, A², A³ and A⁴ each, independently of one another,identically or differently, denotes: a) trans-1,4-cyclohexylene orcyclohexenylene, in which, in addition, one or more non-adjacent CH₂groups may be replaced by —O— and/or —S—, and in which H may besubstituted by F, b) 1,4-phenylene, in which one or two CH groups may bereplaced by N, and in which, in addition, one or more H atoms may bereplaced by Br, Cl, F, CN, methyl, methoxy or a mono- or polyfluorinatedmethyl or methoxy group, or c) a radical from the group1,4-bicyclo[2.2.2]octylene, piperidine-1,4-diyl, cyclobut-1,3-diyl,spiro[3.3]heptane-2,6-diyl,

in which one or more hydrogen atoms may be replaced by F, CN, SCN, SF₅,CH₂F, CHF₂, CF₃, OCH₂F, OCHF₂ or OCF₃, one or more CH groups may bereplaced by N, one or more double bonds may be replaced by single bonds,M denotes —O—, —S—, —CH₂—, —CHY— or —CYY¹—, and Y and Y¹ denote Cl, F,CN, OCF₃ or CF₃, V denotes H or F, Z¹, Z² and Z³ each, independently ofone another, identically or differently, denote a single bond, —CH₂O—,—(CO)O—, —CF₂O—, —CH₂CH₂CF₂O—, —CF₂CF₂—, —CH₂CF₂—, —CH₂CH₂—, —(CH₂)₄—,—CH═CH—, —CH═CF—, —CF═CF— or —C≡C—, where asymmetrical bridges may beoriented to both sides, a denotes 0, 1 or 2, b denotes 0, 1, 2 or 3, andc denotes 0, 1 or 2, where a+b+c≦4; and one or more compounds selectedfrom the formulae IV-VIII, XIII-XVI, D1, D2, XVIIa, XVIIIb, XVIII,XIX-XXV, and XXVII:

in which R⁰ denotes an alkyl or alkoxy radical having 1 to 15 C atoms,where, in addition, one or more CH₂ groups in these radicals are eachoptionally replaced, independently of one another, by —C≡C—, —CF₂O—,—CH═CH—,

 -O—, —(CO)O— or —O(CO)— in such a way that O atoms are not linkeddirectly to one another, and in which, in addition, one or more H atomsare each optionally replaced by halogen, X⁰ denotes F, Cl, CN, SF₅, SCN,NCS, or a halogenated alkyl radical, halogenated alkenyl radical,halogenated alkoxy radical or halogenated alkenyloxy radical, in eachcase having up to 6 C atoms, Y¹⁻⁶ each, independently of one another,denote H or F, Z⁰ denotes —C₂H₄—, —(CH₂)₄—, —CH═CH—, —CF═CF—, —C₂F₄—,—CH₂CF₂—, —CF₂CH₂—, —CH₂O—, —OCH₂—, —COO—, —CF₂O— or —OCF₂—, and, informulae V and VI, Z⁰ also a single bond, b and c each, independently ofone another, denote 0 or 1, R⁵ and R⁶ each, independently of oneanother, denote n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, eachhaving up to 9 C atoms, alkenyl” denotes C₂₋₇-alkenyl.
 2. Aliquid-crystalline medium according to claim 1, wherein said one or morecompounds of formula I are of formula IA

in which R¹, A¹, a, b and V have the meanings indicated for formula I inclaim 1, X denotes F, OCF₃, CN, CF₃, SCN, SF₅, NCS, Cl, OCHF₂, OCHFCF₃,OCF₂CHFCF₃, V denotes H, F or Cl, and L¹, L², L³ and L⁴ each,independently of one another, denote H or F.
 3. A liquid-crystallinemedium according to claim 1, wherein R¹ denotes alkyl, alkoxy, alkenylor alkenyloxy, each having up to 8 carbon atoms.
 4. A liquid-crystallinemedium according to claim 1, wherein L¹ denotes fluorine and L²independently denotes fluorine or hydrogen.
 5. A liquid-crystallinemedium according to claim 1, wherein said one or more compounds offormula I is of formulae I1 to I6:

in which R¹ has the meanings indicated in claim 1, and X denotes F,OCF₃, CN, CF₃, SCN, SF₅, NCS, Cl, OCHF₂, OCHFCF₃, OCF₂CHFCF₃, and L²,L³, L⁴, L⁵ and L⁶, independently of one another, denote H or F.
 6. Aliquid-crystalline medium according to claim 1, wherein L¹ and L² denotefluorine.
 7. A liquid-crystalline medium according to claim 1, wherein Vdenotes hydrogen.
 8. A liquid-crystalline medium according to claim 1,wherein V denotes fluorine.
 9. A liquid-crystalline medium according toclaim 1, wherein said medium further comprises one or more compounds offormulae II and/or III:

in which ring A denotes 1,4-phenylene or trans-1,4-cyclohexylene, a is 0or 1, R³ in each case, independently of one another, denotes alkylhaving 1 to 9 C atoms or alkenyl having 2 to 9 C atoms, and R⁴ in eachcase, independently of one another, denotes an unsubstituted orhalogenated alkyl radical having 1 to 12 C atoms, where, in addition,one or two non-adjacent CH₂ groups are each optionally replaced by —O—,—CH═CH—, —CH═CF—, —(CO)—, —O(CO)— or —(CO)O— in such a way that O atomsare not linked directly to one another.
 10. A liquid-crystalline mediumaccording to claim 1, wherein said medium further comprises one or morecompounds of formulae X, XI and/or XXVI:

in which R⁰ denotes an alkyl or alkoxy radical having 1 to 15 C atoms,where, in addition, one or more CH₂ groups in these radicals are eachoptionally replaced, independently of one another, by —C≡C—, —CF₂O—,—CH═CH—,

—O—, —(CO)O— or —O(CO)— in such a way that O atoms are not linkeddirectly to one another, and in which, in addition, one or more H atomsmay be replaced by halogen,

each, independently of one another, denote

X⁰ denotes F, Cl, CN, SF₅, SCN, NCS, a halogenated alkyl radical,halogenated alkenyl radical, halogenated alkoxy radical or halogenatedalkenyloxy radical, each having up to 6 C atoms, and Y¹, Y², Y³, Y⁴each, independently of one another, denote H or F.
 11. Aliquid-crystalline medium according to claim 1, characterised in thatthe total content of CF₂O-bridged compounds, including the compounds ofthe formula I, is 35% by weight or more.
 12. An electro-opticalliquid-crystal display containing a liquid-crystalline medium accordingto claim
 1. 13. A liquid-crystalline medium according to claim 1,wherein said compounds of formula XII are those selected from thecompounds of formulas XIIa-XIId:

in which alkyl and alkyl* each, independently of one another, denote astraight-chain alkyl radical having 1 to 6 C atoms, and alkenyl andalkenyl* each, independently of one another, denote a straight-chainalkenyl radical having 2 to 6 C atoms.
 14. A liquid-crystalline mediumaccording to claim 1, wherein said compounds of formula XVIII are thoseselected from the compounds of formula XVIIIa:

wherein R^(3a) denotes H, CH₃, C₂H₅ or C₃H₇.
 15. A liquid-crystallinemedium according to claim 1, wherein in the compounds of formulae IV toVIII, X⁰ is F, OCF₃, OCHF₂, CF₃, CF₂H, Cl, or OCH═CF₂, and R⁰ isstraight-chain alkyl or alkenyl, each having up to 6 C atoms.
 16. Aliquid-crystalline medium according to claim 1, wherein in the compoundsof formula IV, R⁰ is alkyl having 1 to 8 C atoms and X⁰ is F, Cl, OCHF₂,OCF₃, or OCH═CF₂.
 17. A liquid-crystalline medium according to claim 1,wherein in the compounds of Formulas XIII-XVI, R⁰ denotes alkyl having 1to 8 C atoms and X⁰ denotes F or Cl.
 18. A liquid-crystalline mediumaccording to claim 1, wherein in the compounds of formulas D1-D2, R⁰denotes alkyl having 1 to 8 C atoms and X⁰ denotes F.
 19. Aliquid-crystalline medium according to claim 1, wherein in the compoundsof formulas XVIIa-XVIIb, R¹ and R² each, independently of one another,denote alkyl having 1 to 8 C atoms, and Y¹ preferably denotes F.
 20. Aliquid-crystalline medium according to claim 1, wherein said mediumcontains 1-15% by weight of compounds of formulas XVIIa-XVIIb.
 21. Aliquid-crystalline medium according to claim 1, wherein in the compoundsof formulas XIX-XXV, X⁰ is F, Cl, CF₃, OCF₃ or OCHF₂, and R⁰ is alkyl,alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 8 C atoms.22. A liquid-crystalline medium according to claim 1, wherein in thecompounds of formula XXVII, R⁰ is an n-butyl radical.